Brush for electric machines

ABSTRACT

Brush for electric machines, comprising a brush body made of carbon, current-carrying fittings, and a spring insulated from the brush body and serving to press the latter against the fittings. The spring may be a flat or a spiral spring; in the latter case a separate pressure element may be interposed.

United States Patent 1 1 Shapiro et al.

BRUSH FOR ELECTRIC MACHINES r j: My: f Z f? 14 1 Jam-28, 1975 1.698.7991/1929 Leland 310/240 1,756,692 4/1930 310/240 2.475.270 6/1949 Briggs310/240 2.013.200 11/1957 Rittcr; 310/247 3075.1 10 1/1903 Pcpworth310/240 3.482.135 12/1909 Hurlin 310/239 Primary Iiraminer-R. SkudyAttorney. Agent. or Firn1Wuters, Roditi. Schwartz & Nisscn [57] ABSTRACTBrush for electric machincs, comprising a brush body made of carbon,current-carrying fittings, and a spring insulated from the brush bodyand serving to press the latter against the fittings. The spring may bea flat or a spiral spring; in the latter case a separate'pressureelement may be interposed.

2 Claims, 4 Drawing Figures 1 BRUSH FOR ELECTRIC MACHINES The presentinvention relates to electric machines and more specifically to brushesfor electric machines.

Known in the art are brushes for electric machines, which comprise abrush body proper, a carbon or graphite rod, and current-carryingfittings with a current-bearing wire affixed thereto.

Also known in the art is a brush (cf., USSR Inventors certificate No.208 I) with split current-carrying fittings, wherein the latter aresecured to the brush by a bolt passing through a hole made in the brush.

This kind of attachment has the following disadvantages: liability toloosening of the bolt connection during vibration of the brush,resulting in worsening of the electrical and thermal contact between thebrush and the fittings, and also inconvenient mounting and dismantlingof the brush due to the necessity of locking the bolt in the tightenedcondition.

Another brush is known in the art (cf. French patent No. 1469006).Herein, the current-carrying fittings are not secured to the brush, butonly pressed to it in the course of operation by means of a spring,which latter simultaneously presses the brush against the surface of therotor. These brushes can be employed for relatively light currents,because the pressure exerted on the brush for its pressing against therotating surface is relatively light, 0.l0.2 kglcm and therefore notable to effect a reliable contact between the fittings and the brush atheavy currents. Beside that, the fact that the brush is not secured tothe fixtures creates a substantial inconvenience in installing andremoving the brush from the brush holder.

It is therefore a general object of the invention to obviate thedisadvantages inherent in the above described prior-art brushes forelectric machines.

It is a specific object of the invention to provide a brush for electricmachines with a split attachment of current-carrying fittings, providingfor a reliable electrical and thermal contact between said fittings andthe brush body proper, and also permitting convenient and quick assemblyof the brush with the fittings and allowing the latter to be usedrepeatedly.

These and other objects are achieved by the provision of a brush forelectric machines, comprising current-carrying fittings attached to thebrush body by means of a spring, wherein the brush is so formed,according to the invention, that one end of the spring is secured to thecurrent-carrying fittings, whereas the other end preferably carries apressure element secured thereto, while the brush body, due to theaction of the spring, is pressed between the current-carrying fittingsand the pressure element, at least the brush spring being insulated fromthe brush body.

It is expedient that an open through slot is made in the brush body, anda spirally threaded hole is made in the current-carrying fittings alongthe axis of the slot, a screw is screwed into said latter hole from theoutside to release the spring.

The spring which presses the brush body between the current-carryingfittings and the pressure element can be made in the form of a coiltension spring positioned in the brush slot.

It is however contemplated by the invention that the above mentionedspring takes the form of a flat spring whose one end is combined withthe pressure element.

In order that the invention may be more clearly understood actual,exemplary embodiments of a brush for electric machine will now be fullydescribed with reference to the accompanying drawings, of which:

FIG. 1 is a longitudinal section of a first exemplary form of a brushfor electric machines, according to the invention;

FIG. 2 is a side view of the same, partly sectionalized;

FIG. 3 is a longitudinal section of another exemplary form of a brushfor electric machines. according to the invention; and

FIG. 4 is a side view of the same. partly sectionalized.

Referring now to FIGS. 1 and 2, an exemplary brush for electric machinesis shown, comprising currentcarrying fittings 2 attached to a graphitebody 3 of a brush 1 by means of a coil latter 4. The spring is screwedwith one end into a threaded hole 5 made in the current-carryingfittings 2, whereas the other end of the spring 4 is applied onto ascrew 6 which performs the function ofa pressure element. The spring 4presses the body 3 of the brush 1 between the current-carrying fittings2 and the head of the screw 6.

To avoid heating of the coil spring 4 by the electric current, thespring is insulated from the brush 1 by means of a washer 7 and a pipe8, both made of an insulating material, the spring 4 being inclosed insaid pipe.

For more convenient mounting and fixing the position of thecurrent-carrying fittings 2, a through slot 9 is made in the graphitebody 3 of the brush 1, which slot accommodates the coil spring 4.

In another embodiment of the brush 1 for electric machines (FIGS. 3, 4),the graphite body 3 of the brush 1 is pressed between thecurrent-carrying fittings 2 and a flat spring 10 which is secured tosaid fittings and carries a pressure element ll secured to its end.Slots 12 are made in the graphite body 3 of the brush 1 to fix inposition the current-carrying fittings 2 and the free end of the spring10.

In this brush 1, the pressure element takes the shape of a strip made ofan insulating material. with the aim of preventing electric current flowthrough the flat spring 10 to preclude heating thereof. Convenienthandling of the graphite body 3 of the brush 1 is effected by aspecially provided fixture (not shown) having a spirally threadedworking part.

In the first form of the brush for electric machines, illustrated inFIGS. 1, 2, wherein the coil spring 4 is employed, the fixture isscrewed into the hole 5 in the current-carrying fittings and into thespring 4, thus extending the latter upon which the body 3 of the brush 1can easily be removed and replaced with another one, if

necessary.

In the second brush form, illustrated in FIGS 3, 4, wherein the flatspring 10 is employed, the fixture is screwed into the hole 5 andpresses off the flat spring 10, thus releasing the body 3 of the brush1.

The above disclosed brushes for electric machines provide for a simpleand reliable fastening of the brush and also for easy replacement of thegraphite body of the brush.

What is claimed is:

l. A brush for electric machines to provide electric contact with amoving part of a machine, comprising a brush body made of carbon andhaving an open through slot; current-carrying fittings on said body andhaving therein a threaded opening; and a spiral tension spring locatedin said slot, one end of said spring being 4 brush body made of carbon;current-carrying fittings; and a flat spring, one end of the latterbeing attached to said fittings; and spring being insulated from saidbrush body, the latter being held between said fittings and the free endof said spring.

1. A brush for electric machines to provide electric contact with amoving part of a machine, comprising a brush body made of carbon andhaving an open through slot; current-carrying fittings on said body andhaving therein a threaded opening; and a spiral tension spring locatedin said slot, one end of said spring being fixed in said threadedopening, while the other end of said spring is applied onto a pressureelement; said spring and said pressure element being inSulated from saidbrush body, the latter being held tightly between said fittings and saidpressure element.
 2. A brush for electric machines to provide electriccontact with a moving part of a machine, comprising a brush body made ofcarbon; current-carrying fittings; and a flat spring, one end of thelatter being attached to said fittings; and spring being insulated fromsaid brush body, the latter being held between said fittings and thefree end of said spring.